Seasonal Phenology and Colony Longevity Patterns in a Predatory Social Wasp

Abstract. Social wasps play critical ecological roles in an ecosystem, providing a diversity of services and some disservices. Yellowjacket wasps (Vespula spp.) in particular are well known for shaping arthropod communities via predation and competition for resources. In part due to their sociality and large colony sizes, Vespula can have a profound ecological impact on local communities. Such effects can be magnified when colonies exhibit a perennial life history, in which a colony will overwinter, persist for more than one year, and become orders of magnitude larger in size compared to typical annual colonies. Despite growing interest in the factors that influence colony success, we currently lack the ability to predict when yellowjackets may have a high-abundance or outbreak year. This highlights the need for a critical understanding of the phenological patterns of foraging activity, colony distribution, and senescence. Here, we quantify the seasonal activity and foraging rates of 123 colonies of the western yellowjacket, V. pensylvanica, in its native range over 4 consecutive years. Average colony longevity was about 1 month longer than previously reported for this species, and colonies with later peaks in activity and higher average traffic rates persisted longer into the winter. Longer-lived colonies tended to cluster together within a year, but not between years. We found 3 perennial colonies (2.4% of all colonies), and they exhibited tenfold higher peak traffic rates compared to annual colonies. By identifying temporal and spatial patterns in survivorship and colony longevity, we gain insight into the factors associated with prolonged survival time and increased likelihood of overwintering in yellowjacket wasps.